Dynamic braking of series motors



P 1949- E. B. ANKENMAN 2,482,453

DYNAMIC BRAKING OF SERIES MOTORS Filed July 17, 1948 lo 3 D1 4 SF A ll l2 a:

WITNESSES: INVENTQR flyf/d EcrlB.Ankenmon.

ATTORNEY Patented Sept. 20,- 1949 Burg-h, P

\ seams Morons T ration-,1 East Pitts- I l ation' df Pennsylvania current motors with simple, non-movable means.

A more specific object of my invention is the use of an extremely simple circuit including no more than two rectifiers for effecting dynamic braking of a series direct current motor.

Other objects and advantages will become more apparent from a study of the following specification and the drawing forming a part of my disclosure, and in which drawing the single figure illustrates diagrammatically my invention as applied to a series direct current motor.

In the single figure of the drawing, M designates the motor having an armature winding A and having the series field winding SF. The main contactor C includes the main contacts 8 and I2, the dynamic braking contacts 15, and the holding contacts 1. One of the important features of my invention is the simplification to the point that a single contactor sufiices for establishing the dynamic braking circuit. With prior art schemes usually three and often more than three contactors were necessary for effecting dynamic braking of a series motor.

' Probably the best method of describing the merits of my invention is by means of a description of a complete operating cycle.

When the motor M is to be started the attendant actuates the starting push-button 4, whereupon a circuit is established from the positively energized conductor I through the pushbutton 2, the actuating coil 3 of the main contactor C, the starting push-button 4, and conductor 5 to the negatively energized conductor 6.

The operation of contactor C effects the closing of contacts I, 8 and 12. The closing of contacts 1 establishes a shunt circuit for the starting push-button 4 to thus effect holding-in, or continued energization of actuating coil 3.

The closing of contacts 8 and I2 establishes a circuit for the motor M that may be traced from conductor 1 through contacts 8, conductor 9, series field SF, rectifier l0, the armature wind- (o1. m rrow 5 1' i e er s ,t imigiltaiieoiisfsilos f ,3)? rftaste is and dseniirg er areas 1; rare ff;

When contacts I5 are closed, the energization of the series field SF is maintained from the motor armature A by a circuit that may be traced from the upper armature terminal through the rectifier l3, conductor 9, series field SF, the dynamic braking resistor [4, contacts I5, and conductor I l to the negative terminal of armature A.

It will be noted that the energy stored in the armature and the series field will be dissipated in the dynamic braking resistor H and due to the fact that the direction of the current in the series field SF is not changed but follows the alternate path through the rectifier, the flux in the fieldv remains in the same direction and is supported by the current in the dynamic braking circuit.

Further, it should be noted that the alternate path includes but one rectifier, as l3, and that the normal operating circuit includes but one rectifier, as H).

In efiect I thus provide among other features a method of and apparatus for obtaining dynamic braking of a series motor through the use of half wave rectifiers to redirect the current through the series field SF in the same direction during the braking sequence. The rectifiers may be selected of the simplest type as copper oxide rectifi'ers to thus avoid the use of any moving parts.

While I have shown but a single embodiment of my invention, I do not consider the invention limited to the particular showing made, since modifications within the spirit of the invention can readily be made by those skilled in the art particularly after having had the benefit of the teachings of my invention.

I claim as my invention:

1. In apparatus for effecting the stopping of a series direct current motor by dynamic braking, in combination, a series motor having an armature winding and a series field winding, a loop circuit including the series field winding, a first rectfier, and a second rectifier, a contactor having an actuated, or pick-up position, and a dropout position, a dynamic braking circuit including the motor armature winding, the second rectifier, the series field winding, a dynamic braking resistor, and switching contacts coupled to be operable by the contactor and which are normally closed when the contactor is in its drop-out position, motor energizing contact for the contactor normally closed when the contactor is in its pickup position to thus connect the positive and negative supply terminals, respectively, to the connection between the series field winding and the second rectifier, and the connection between the armatureand the switching contacts.

2. In apparatus for effecting the stopping of a series direct current motor by dynamic braking, in combination, a series motor having armature windings and series field windings, a motor energizing circuit including a positive supply terminal, contacts, the series field winding, a first rectifier for conducting current in the direction of the recitation of this circuit, a first motor armature terminal, the motor armature winding,

a second motor armature terminal, contacts, and

tactor means to non-operated position, said dynamic braking circuit including the first motor armature terminal, a second rectifier for conducting current in the direction of the recitation of this circuit, the series field winding, the dynamic braking resistor, the dynamic braking contacts, the second motor armature terminal and said motor armature to said first motor armature terminal.

3. A dynamic braking scheme for a series direct current motor, comprising, a dynamic braking circuit including a first motor armature terminal, normally the terminal of positive counter electromotive force, a first rectifier connected to allow current to flow in the direction of the recitation of this circuit, a series field winding, a dynamic braking impedance, a switch normally closed during dynamic braking, the second or negative motor terminal, and the motor armature winding to the first motor armature terminal, and means for connecting positive potential to the connection between the first rectifier and the series field and negative potential to the second motor armature terminal, and a second rectifier for conducting current from the connection between the series held and the dynamic braking impedance and the first motor armature terminal.

EARL B. ANKENMAN.

No references cited. 

